The infestation of the mediterranean fruit fly and the continued problem with the gypsy moth are clear indications that current methods of insect pest management are proving to be inadequate. A suggested alternative method of insect control is disruption of the development of the insect by interference with the endocrine systems involved, an obvious candidate being the neuropeptide prothoracicotropic hormone (PTTH). Diapause, a state of developmental arrest which occurs in response to environmental conditions unfavorable for growth and development, is a state particularly well-suited for an investigation of this approach since it is endocrinologically regulated and since its occurrence is critical for the survival of the insect. The three classes of hormones that regulate insect postembryonic development - PTTH, ecdysteroids and juvenile hormones (JH) - are also thought to control diapause, but the endocrine mechanisms involved are poorly understood. The objective of this proposal is to elucidate the endocrinology of diapause so that the role of these hormones can be established and in this way obtain essential information requisite to the formulation of a means of insect control by manipulating the endocrine system at this critical stage of development. Manduca sexta, a lepidopteran that undergoes a photoperiodically-controlled pupal diapause, is the animal for these studies. The endocrinology of its nondiapause development is established, permitting its comparative evaluation with the endocrinology of diapause development. The proposed research will focus on the endocrine physilogy of diapause induction. Aspects of diapause endocrinology to be investigated are: (1) hemolymph titers of the hormones; (2) fluctuations in their rates of synthesis; (3) release of the hormones, particularly PTTH; and (4) metabolism. Since the hormones involved appear to exist in multiple forms, their quantitative and qualitative characteristics will be examined. Contemporary methods such as RIA, in vitro culture and HPLC will be utilized in the analysis of these hormones. The basic endocrinology established will define for the first time the relationships that exist among the PTTHs, ecdysteroids and JHs during diapause, which should permit a determination of the endocrine mechanisms which are causal to this process.